Refrigeration cycle apparatus

ABSTRACT

A refrigeration cycle apparatus includes a circulation path in which a working fluid containing 1,1,2-trifluoroethylene is circulated from a compressor through a condenser, an expansion valve and an evaporator back to the compressor. The refrigeration cycle apparatus includes a composition change detection unit, a composition adjustment unit, and a control unit. The composition change detection unit detects a change of a composition of the working fluid from a steady composition thereof. The composition adjustment unit adjusts the composition of the working fluid. The control unit controls the composition adjustment unit based on a detection result obtained by the composition change detection unit.

TECHNICAL FIELD

The present invention relates to a refrigeration cycle apparatus using a working fluid containing 1,1,2-trifluoroethylene.

BACKGROUND ART

In a refrigeration cycle apparatus such as an air-conditioner or a refrigerator, a hydrofluorocarbon (HFC) based refrigerant has been widely used as a working refrigerant. However, HFCs have a high global warming potential (GWP). Thus, it is pointed out that HFCs may cause global warming. It is therefore imperative to develop a working fluid for refrigeration cycles, which has less influence on the ozone layer and has a low GWP. A working fluid containing a hydrofluoroolefin (HFO) having a carbon-carbon double bond which is likely to be decomposed by OH radicals in the air has been studied as a working fluid for refrigeration cycles having less influence on the ozone layer and having less influence on global warming. Patent Document 1 discloses a refrigeration cycle apparatus using a working fluid containing 1,1,2-trifluoroethylene (HFO-1123).

CITATION LIST Patent Document

Patent Document 1: JP-A-2015-145452

Patent Document 2: JP-A-H11-14200

SUMMARY OF THE INVENTION Technical Problems

In a refrigeration cycle apparatus, a refrigerator oil which is highly compatible with a working fluid is stored inside a compressor in order to prevent seizure. During operation of the refrigeration cycle apparatus, a part of the refrigerator oil is discharged to the outside of the compressor together with the working fluid. The refrigerator oil discharged to the outside of the compressor stays in an accumulator or the like provided on the suction side of the compressor during the operation of the refrigeration cycle apparatus. When the amount of the refrigerator oil is insufficient inside the compressor, a problem such as seizure in the compressor arises. In order to prevent a fixed amount or more of the refrigerator oil from staying outside the compressor, an oil returning mechanism is provided in the refrigeration cycle apparatus. Example of the oil returning mechanism include an oil returning hole provided in an outlet pipe in the accumulator and the like (Patent Document 2 or the like).

During the operation of the refrigeration cycle apparatus, the following phenomenon so-called stagnation may occur: the working fluid is dissolved into the refrigerator oil staying outside the compressor, e.g. in the accumulator or the like. When the working fluid contains HFO-1123 and a component other than HFO-1123, the component other than HFO-1123 may have a higher degree of solubility to the refrigerator oil than HFO-1123 depending on the kind of the component other than HFO-1123 when the temperature of the refrigerator oil is low. In such a case, for example, when the ambient temperature is low during the operation, the component other than HFO-1123 is selectively dissolved into the refrigerator oil which has been cooled down to a low temperature by the ambient air. That is, during the operation of the refrigeration cycle apparatus, even if the refrigerator oil is maintained by the oil returning mechanism described in Patent Document 2 or the like so that a fixed amount or more of the refrigerator oil is prevented from staying outside the compressor, the proportion of HFO-1123 in the working fluid circulating within the refrigeration cycle may be increased due to change in conditions such as the ambient temperature.

Further, when a non-azeotropic refrigerant or a pseudoazeotropic refrigerant is used as the working fluid in the refrigeration cycle apparatus, refrigerant components contained in the working fluid have different boiling points from one another. Therefore, a high-boiling-point refrigerant component stays as a liquid refrigerant more easily than a low-boiling-point refrigerant component at a place where the liquid refrigerant tends to stay within the refrigeration cycle apparatus, such as the accumulator or a receiver. For example, in a case where the working fluid containing HFO-1123 is used in the refrigeration cycle apparatus, when HFO-1123 has the lowest boiling point among refrigerant components, the components other than HFO-1123 stay as liquid refrigerants in the accumulator, the receiver or the like more easily than HFO-1123. As a result, the proportion of HFO-1123 in the working fluid circulating within the refrigeration cycle may be increased.

It has been known that a chain of chemical reactions called a disproportionation reaction (self-decomposition reaction) with heat generation may occur when energy is applied to HFO-1123 in a high-temperature and high-pressure state. Such a disproportionation reaction is a chemical reaction in which two or more molecules belonging to the same kind react with each other to generate two or more different kinds of products. When the working fluid containing HFO-1123 is used in the refrigeration cycle apparatus, it is necessary to keep the proportion of HFO-1123 in the working fluid circulating within the refrigeration cycle not higher than a predetermined value, in order to reduce the risk that the disproportionation reaction of HFO-1123 occurs. When the proportion of HFO-1123 in the working fluid circulating within the refrigeration cycle increases due to change in conditions such as the ambient temperature during the operation of the refrigeration cycle apparatus, the risk that the disproportionation reaction of HFO-1123 occurs increases.

The present invention has been developed in consideration of the aforementioned situation. An object of the present invention is to provide a refrigeration cycle apparatus capable of effectively preventing occurrence of disproportionation reaction of HFO-1123 when a working fluid containing FIFO-1123 is used.

Solution to Problems

The refrigeration cycle apparatus in the first embodiment of the present invention is a refrigeration cycle apparatus comprising a circulation path in which a working fluid containing 1,1,2-trifluoroethylene is circulated from a compressor through a condenser, an expansion valve and an evaporator back to the compressor, the refrigeration cycle apparatus comprising:

a composition change detection unit which detects a change of a composition of the working fluid from a steady composition thereof;

a composition adjustment unit which adjusts the composition of the working fluid; and

a control unit which controls the composition adjustment unit,

wherein the control unit controls the composition adjustment unit based on a detection result obtained by the composition change detection unit.

In the refrigeration cycle apparatus in the second embodiment of the present invention, the composition change detection unit is a discharge temperature sensor which detects a discharge temperature of the compressor, and judges that the composition of the working fluid is changed from the steady composition when the discharge temperature detected by the discharge temperature sensor exceeds a predetermined temperature.

In the refrigeration cycle apparatus in the third embodiment of the present invention, the composition change detection unit is a superheat detection unit which detects a superheating degree of the working fluid sucked into the compressor, and judges that the composition of the working fluid is changed when the superheating degree detected by the superheat detection unit exceeds a predetermined value.

In the refrigeration cycle apparatus in the fourth embodiment of the present invention, the composition change detection unit is a subcool detection unit which detects a subcooling degree of the working fluid sucked into the compressor, and judges that the composition of the working fluid is changed when the subcooling degree detected by the subcool detection unit is deviated from a predetermined range.

The refrigeration cycle apparatus in the fifth embodiment of the present invention further comprises an accumulator provided between the evaporator and the compressor in the circulation path for storing an excess of the working fluid, and

the composition adjustment unit is a heater attached to the accumulator, and

the control unit allows electric current to flow through the heater when the composition change detection unit judges that the composition of the working fluid is changed.

The refrigeration cycle apparatus in the sixth embodiment of the present invention further comprises an accumulator provided between the evaporator and the compressor in the circulation path for storing an excess of the working fluid, and

the composition adjustment unit includes: a hot gas bypass which diverts a part of a hot gas discharged from the compressor and introduces the diverted hot gas into the accumulator; and an on-off valve provided in the hot gas bypass, and

the control unit controls the on-off valve so as to change a state of the on-off valve from a closed state to an open state when the composition change detection unit judges that the composition of the working fluid is changed.

In the refrigeration cycle apparatus in the seventh embodiment of the present invention, the composition adjustment unit is a motor which drives a compression mechanism of the compressor, and the control unit controls the motor so as to increase the number of revolutions of the motor when the composition change detection unit judges that the composition of the working fluid is changed.

In the refrigeration cycle apparatus in the eighth embodiment of the present invention, the composition adjustment unit is the expansion valve, and the control unit controls the expansion valve so as to increase an opening degree of the expansion valve when the composition change detection unit judges that the composition of the working fluid is changed.

The refrigeration cycle apparatus in the ninth embodiment of the present invention further comprises a receiver provided between the condenser and the expansion valve in the circulation path for storing an excess of the working fluid, and

the composition adjustment unit includes a liquid refrigerant bypass for extracting a liquid refrigerant stored in the receiver and injecting the extracted liquid refrigerant to an intermediate pressure portion of the compressor through an auxiliary expansion valve, and

the control unit controls the auxiliary expansion valve so as to increase an opening degree of the auxiliary expansion valve when the composition change detection unit judges that the composition of the working fluid is changed.

Advantageous Effects of the Invention

According to the present invention, it is possible to effectively prevent occurrence of disproportionation reaction of HFO-1123 when a working fluid containing HFO-1123 is used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram illustrating a refrigeration cycle apparatus in one example.

FIG. 2 is a temperature-entropy chart illustrating the state change of a working fluid in the refrigeration cycle apparatus.

FIG. 3 is a pressure-enthalpy chart illustrating the state change of a working fluid in the refrigeration cycle apparatus.

FIG. 4 is a view of a schematic configuration of an accumulator.

FIG. 5 is a block diagram illustrating a schematic configuration of a composition adjustment mechanism which adjusts a composition of a working fluid circulating within a refrigeration cycle.

FIG. 6 is a diagram for explaining a superheat detection unit as the composition change detection unit in Modification example 1.

FIG. 7 is a diagram for explaining a superheat detection unit as the composition change detection unit in Modification example 2.

FIG. 8 is a diagram for explaining a hot gas introduction unit as the composition adjustment unit in Modification example 3.

FIG. 9 is a view of a schematic configuration of an accumulator to which a hot gas bypass as the hot gas introduction unit is connected.

FIG. 10 is a diagram for explaining a composition adjustment unit in Modification example 4.

FIG. 11 is a diagram for explaining a composition adjustment unit in Modification example 5.

FIG. 12 is a diagram for explaining a composition adjustment unit in Modification example 6.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention are described below with reference to the drawings.

First, description is made about a working fluid for use in a refrigeration cycle apparatus in the present invention.

<Working Fluid> (HFO-1123)

A working fluid used in the present invention contains 1,1,2-trifluoroethylene (HFO-1123).

First, description is made about the working fluid for use in the refrigeration cycle apparatus in the present invention.

The properties of HFO-1123 as working fluid are shown in Table 1 particularly by relative comparison with R410A (a pseudoazeotropic mixture refrigerant of HFC-32 and HFC-125 in a mass ratio of 1:1). Cycle performance is evaluated by a coefficient of performance and refrigeration capacity obtained by the later-described methods. The coefficient of performance and the refrigeration capacity of HFO-1123 are expressed by relative values (hereinafter referred to as relative coefficient of performance and relative refrigeration capacity) based on those of R410A as reference (1.000). The global warming potential (GWP) is a 100-years value shown in Intergovernmental Panel on Climate Change (IPCC), Fourth assessment report (2007), and measured in accordance with the method of the same report. In the present specification, GWP means the value unless otherwise specified. When the working fluid is formed of a mixture, the temperature gradient is a significant factor for evaluating the working fluid, as is described later. It is preferable that the value of the temperature gradient is smaller.

TABLE 1 R410A HFO-1123 Relative coefficient of performance 1.000 0.921 Relative refrigeration capacity 1.000 1.146 Temperature gradient [° C.] 0.2 0 GWP 2088 0.3

[Optional Components]

The working fluid used in the present invention preferably contains HFO-1123. In addition to HFO-1123, optional compounds that are usually used as working fluids may be contained as long as they do not impair the effect of the present invention. Examples of such optional compounds (optional components) include HFCs, HFOs (HFCs each having a carbon-carbon double bond) other than HFO-1123, and other components that can be liquefied or vaporized together with HFO-1123. Preferred optional components are HFCs, and HFOs (HFCs each having a carbon-carbon double bond) other than HFO-1123.

Such an optical component is preferably a compound which can set the GWP or the temperature gradient within an acceptable range while enhancing the relative coefficient of performance and the relative refrigeration capacity when it is, for example, used in a heat cycle together with HFO-1123. When the working fluid contains such a compound together with HFO-1123, better cycle performance can be obtained while keeping the GWP low, and the influence of the temperature gradient can be reduced.

(Temperature Gradient)

When the working fluid contains, for example, HFO-1123 and an optical component, the working fluid has a significant temperature gradient as long as HFO-1123 and the optional component do not form an azeotropic composition. The temperature gradient of the working fluid depends on the kind of the optional component and the mixture ratio between HFO-1123 and the optional component.

Usually, when a mixture is used as the working fluid, an azeotropic mixture or a pseudoazeotropic mixture such as R410A is preferably used. A non-azeotropic composition has a problem that a change in composition occurs when the composition is charged into a refrigerator/air-conditioner from a pressure vessel. Further, when a refrigerant leaks from the refrigerator/air-conditioner, there is an extremely great possibility that the composition of the refrigerant within the refrigerator/air-conditioner may change so that the composition of the refrigerant cannot be recovered to its initial state easily. On the other hand, the problem can be avoided by using an azeotropic or pseudoazeotropic mixture as the working fluid.

The “temperature gradient” is generally used as an index to evaluate availability of a mixture in the working fluid. The temperature gradient is defined as such a property that the initiation temperature and the completion temperature of evaporation in a heat exchanger such as an evaporator or of condensation in a heat exchanger such as a condenser differ from each other. The temperature gradient is 0 in an azeotropic mixture, and the temperature gradient is very close to 0 in a pseudoazeotropic mixture, for example, the temperature gradient of R410A is 0.2.

When the temperature gradient is large, there is a problem that the inlet temperature, for example, in the evaporator decreases so that frosting is more likely to occur. Further, generally in a heat cycle system, a working fluid flowing in a heat exchanger and a heat source fluid such as water or air are made to flow as counter-current flows against each other in order to improve the heat exchange efficiency. Since the temperature difference of the heat source fluid is small in a stable operation state, it is difficult to obtain a heat cycle system with a good energy efficiency when a non-azeotropic mixture fluid with a large temperature gradient is used. Accordingly, when a mixture is used as the working fluid, it is desired that the working fluid has an appropriate temperature gradient.

(HFC)

As the HFC as the optional component, it is preferable to select an HFC from the aforementioned viewpoint. Here, an HFC is known to have a high GWP as compared with HFO-1123. Accordingly, as the HFC used in combination with HFO-1123, it is preferable to select an HFC appropriately in order not only to improve cycle performance as the working fluid and set the temperature gradient within a proper range but also to adjust particularly the GWP within an acceptable range.

As an HFC which has less influence on the ozone layer and which has less influence on global warming, an HFC having 1 to 5 carbon atoms is specifically preferred. The HFC may be linear, branched or cyclic.

Examples of the HFC include HFC-32, difluoroethane, trifluoroethane, tetrafluoroethane, HFC-125, pentafluoropropane, hexafluoropropane, heptafluoropropane, pentafluorobutane, heptafluorocyclopentane and the like.

Among them, in view of less influence on the ozone layer and excellent refrigeration cycle performance, preferable examples of the HFC include HFC-32, 1,1-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC-143a), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane (HFC-134a) and HFC-125, and more preferable examples thereof include HFC-32, HFC-152a, HFC-134a and HFC-125.

One kind of HFC may be used alone or two or more kinds of HFCs may be used in combination.

The content of the HFC in the working fluid (100 mass %) may be desirably selected depending on required properties of the working fluid. When the working fluid is, for example, made of HFO-1123 and HFC-32, the coefficient of performance and the refrigeration capacity can be improved when the content of HFC-32 falls within the range of from 1 to 99 mass %. When the working fluid is made of HFO-1123 and HFC-134a, the coefficient of performance can be improved when the content of HFC-134a falls within the range of from 1 to 99 mass %.

With respect to GWP of the aforementioned preferred HFC, GWP of HFC-32 is 675, GWP of HFC-134a is 1,430, and GWP of HFC-125 is 3,500. In order to reduce the GWP of the obtainable working fluid, HFC-32 is the most preferable HFC as the optional component.

HFO-1123 and HFC-32 can form a pseudoazeotropic mixture close to an azeotropic mixture when the mass ratio between the both is from 99:1 to 1:99. The mixture of the both has a temperature gradient close to 0 substantially without selecting a composition range thereof. Also with respect to this point, HFC-32 is advantageous as an HFC to be combined with HFO-1123.

When HFC-32 is used together with HFO-1123 in the working fluid used in the present invention, specifically the content of HFC-32 based on 100 mass % of the working fluid is preferably 20 mass % or more, more preferably from 20 to 80 mass %, and further preferably from 40 to 60 mass %.

When the working fluid used in the present invention, for example, contains HFO-1123, an HFO other than HFO-1123 is preferably HFO-1234yf (GWP=4), HFO-1234ze(E) or HFO-1234ze(Z) (GWP=6 in both the (E)-isomer and the (Z)-isomer), and more preferably HFO-1234yf or HFO-1234ze(E) because they are high in critical temperature and excellent in durability and coefficient of performance. One kind of HFOs other than HFO-1123 may be used alone, or two or more kinds of them may be used in combination. The content of the HFO other than HFO-1123 in the working fluid (100 mass %) may be desirably selected depending on required properties of the working fluid. When the working fluid is, for example, made of HFO-1123 and HFO-1234yf or HFO-1234ze, the coefficient of performance can be improved when the content of HFO-1234yf or HFO-1234ze falls within the range of from 1 to 99 mass %.

When the working fluid used in the present invention contains HFO-1123 and HFO-1234yf, a preferred composition range is shown below as a composition range (S).

In the respective formulae showing the composition range (S), the abbreviation of each compound designates the proportion (mass %) of the compound to the total amount of HFO-1123, HFO-1234yf and other components (HFC-32 and the like).

<Composition Range (S)>

HFO-1123+HFO-1234yf≥70 mass %

95 mass %≥HFO-1123/(HFO-1123+HFO-1234yf)≥35 mass %

The working fluid in the composition range (S) is extremely low in GWP and small in temperature gradient. In addition, refrigeration cycle performance high enough to replace the R410A in the background art can be exhibited also from the viewpoint of the coefficient of performance, the refrigeration capacity and the critical temperature.

In the working fluid in the composition range (S), the proportion of HFO-1123 to the total amount of HFO-1123 and HFO-1234yf is more preferably from 40 to 95 mass %, further more preferably from 50 to 90 mass %, particularly preferably from 50 to 85 mass %, and most preferably from 60 to 85 mass %.

In addition, the total content of HFO-1123 and HFO-1234yf in 100 mass % of the working fluid is more preferably from 80 to 100 mass %, further more preferably from 90 to 100 mass %, and particularly preferably from 95 to 100 mass %.

In addition, it is preferable that the working fluid used in the present invention contains HFO-1123, HFC-32 and HFO-1234yf. A preferred composition range (P) in a case where the working fluid contains HFO-1123, HFO-1234yf and HFC-32 is shown below.

In the respective formulae showing the composition range (P), the abbreviation of each compound designates the proportion (mass %) of the compound to the total amount of HFO-1123, HFO-1234yf and HFC-32. The same thing can be also applied to the composition range (R), the composition range (L) and the composition range (M). In addition, in the following composition range, it is preferable that the total amount of HFO-1123, HFO-1234yf and HFC-32 described specifically is more than 90 mass % and 100 mass % or less based on the entire amount of the working fluid for heat cycle.

<Composition Range (P)>

70 mass %≤HFO-1123+HFO-1234yf

30 mass %≤HFO-1123≤80 mass %

0 mass %<HFO-1234yf≤40 mass %

0 mass %<HFC-32≤30 mass %

HFO-1123/HFO-1234yf≤95/5 mass %

The working fluid having the aforementioned composition is a working fluid having respective properties of HFO-1123, HFO-1234yf and HFC-32 in a balanced manner, and having less defects of the respective components. That is, the working fluid is a working fluid which has an extremely low GWP, and has a small temperature gradient and a certain performance and efficiency when used for heat cycle, and thus, favorable cycle performance is obtained by the working fluid. Here, it is preferable that the total amount of HFO-1123 and HFO-1234yf is 70 mass % or more based on the total amount of HFO-1123, HFO-1234yf and HFC-32.

A more preferred composition as the working fluid used in the present invention may be a composition containing HFO-1123 in an amount of from 30 to 70 mass %, HFO-1234yf in an amount of from 4 to 40 mass %, and HFC-32 in an amount of from 0 to 30 mass %, based on the total amount of HFO-1123, HFO-1234yf and HFC-32 and having a content of HFO-1123 in an amount of 70 mol % or less based on the entire amount of the working fluid. The working fluid within the aforementioned range is a working fluid in which self-decomposition reaction of HFO-1123 is inhibited to enhance the durability in addition to the aforementioned effect enhanced. From the viewpoint of the relative coefficient of performance, the content of HFC-32 is preferably 5 mass % or more, and more preferably 8 mass % or more.

Other preferred compositions in the case where the working fluid used in the present invention contains HFO-1123, HFO-1234yf and HFC-32 are shown below. A working fluid in which self-decomposition reaction of HFO-1123 is inhibited to enhance the durability can be obtained as long as the content of HFO-1123 is 70 mol % or less based on the entire amount of the working fluid.

A more preferred composition range (R) is shown below.

<Composition Range (R)>

10 mass %≤HFO-1123<70 mass %

0 mass %<HFO-1234yf≤50 mass %

30 mass %<HFC-32≤75 mass %

The working fluid having the aforementioned composition is a working fluid having respective properties of HFO-1123, HFO-1234yf and HFC-32 in a balanced manner, and having less defects of the respective components. That is, the working fluid is a working fluid which has a low GWP and ensures durability while having a small temperature gradient and having a high performance and efficiency when used for heat cycle, and thus, favorable cycle performance is obtained by the working fluid.

A preferred range in the working fluid having the composition range (R) is shown below.

20 mass %≤5 HFO-1123<70 mass %

0 mass %<HFO-1234yf≤40 mass %

30 mass %<HFC-32≤75 mass %

The working fluid having the aforementioned composition is a working fluid having respective properties of HFO-1123, HFO-1234yf and HFC-32 in a balanced manner, and having less defects of the respective components. That is, the working fluid is a working fluid which has a low GWP and ensures durability, while having a smaller temperature gradient and having higher performance and efficiency when used for heat cycle, and thus, favorable cycle performance is obtained by the working fluid.

A more preferable range (L) in the working fluid having the composition range (R) is shown below. A composition range (M) is further more preferable.

<Composition Range (L)>

10 mass %≤HFO-1123<70 mass %

0 mass %<HFO-1234yf≤50 mass %

30 mass %<HFC-32≤44 mass %

<Composition Range (M)>

20 mass %≤HFO-1123<70 mass %

5 mass %≤HFO-1234yf≤40 mass %

30 mass %<HFC-32≤44 mass %

The working fluid in the composition range (M) is a working fluid having respective properties of HFO-1123, HFO-1234yf and HFC-32 in a balanced manner, and having less defects of the respective components. That is, the working fluid is a working fluid in which an upper limit of GWP is reduced to 300 or less and durability is ensured, and which has a small temperature gradient smaller than 5.8 and has a relative coefficient of performance and a relative refrigeration capacity close to 1 when used for heat cycle, and thus, favorable cycle performance is obtained by the working fluid.

Within this range, the upper limit of the temperature gradient is decreased, and the lower limit of the product of the relative coefficient of performance and the relative refrigeration capacity is increased. In order to increase the relative coefficient of performance, it is more preferable to satisfy “8 mass %≤HFO-1234yf”. In addition, in order to increase the relative refrigeration capacity, it is more preferable to satisfy “HFO-1234yf≤35 mass %”.

In addition, it is preferable that another working fluid used in the present invention contains HFO-1123, HFC-134a, HFC-125 and HFO-1234yf. With this composition, flammability of the working fluid can be controlled.

More preferably, in the working fluid containing HFO-1123, HFC-134a, HFC-125 and HFO-1234yf, the proportion of the total amount of HFO-1123, HFC-134a, HFC-125 and HFO-1234yf is more than 90 mass % and 100 mass % or less based on the entire amount of the working fluid, and the proportion of HFO-1123 is 3 mass % or more and 35 mass % or less, the proportion of HFC-134a is 10 mass % or more and 53 mass % or less, the proportion of HFC-125 is 4 mass % or more and 50 mass % or less, and the proportion of HFO-1234yf is 5 mass % or more and 50 mass % or less, based on the total amount of HFO-1123, HFC-134a, HFC-125 and HFO-1234yf. Such a working fluid is a working fluid being non-flammable, having excellent safety, having less influence on the ozone layer and global warming, and having excellent cycle performance when used for a heat cycle system.

Most preferably, in the working fluid containing HFO-1123, HFC-134a, HFC-125 and HFO-1234yf, the proportion of the total amount of HFO-1123, HFC-134a, HFC-125 and HFO-1234yf is more than 90 mass % and 100 mass % or less based on the entire amount of the working fluid, and the proportion of HFO-1123 is 6 mass % or more and 25 mass % or less, the proportion of HFC-134a is 20 mass % or more and 35 mass % or less, the proportion of HFC-125 is 8 mass % or more and 30 mass % or less, and the proportion of HFO-1234yf is 20 mass % or more and 50 mass % or less, based on the total amount of HFO-1123, HFC-134a, HFC-125 and HFO-1234yf. Such a working fluid is a working fluid being non-flammable, having more excellent safety, having much less influence on the ozone layer and global warming, and having more excellent cycle performance when used for a heat cycle system.

(Other Optional Components)

The working fluid used in a composition for a heat cycle system in the present invention may contain carbon dioxide, a hydrocarbon, a chlorofluoroolefin (CFO), a hydrochlorofluoroolefin (HCFO) and the like, other than the aforementioned optional component. As the other optional component, a component which has less influence on the ozone layer and has less influence on global warming is preferred.

Examples of the hydrocarbon include propane, propylene, cyclopropane, butane, isobutane, pentane, isopentane and the like.

One kind of such hydrocarbons may be used alone or two or more kinds of them may be used in combination.

When the working fluid contains a hydrocarbon, its content is less than 10 mass %, preferably from 1 to 5 mass %, and more preferably from 3 to 5 mass %, based on 100 mass % of the working fluid. When the content of the hydrocarbon is equal to or more than the lower limit, the solubility of a mineral refrigerator oil in the working fluid is more favorable.

Examples of the CFO include chlorofluoropropene, chlorofluoroethylene and the like. In order to easily control the flammability of the working fluid without significantly decreasing the cycle performance of the working fluid, the CFO is preferably

-   1,1-dichloro-2,3,3,3-tetrafluoropropene (CFO-1214ya), -   1,3-dichloro-1,2,3,3-tetrafluoropropene (CFO-1214yb) or -   1,2-dichloro-1,2-difluoroethylene (CFO-1112).

One kind of such CFOs may be used alone or two or more kinds of them may be used in combination.

When the working fluid contains the CFO, its content is less than 10 mass %, preferably from 1 to 8 mass %, and more preferably from 2 to 5 mass %, based on 100 mass % of the working fluid. When the content of the CFO is equal to or more than the lower limit, the flammability of the working fluid can be easily controlled. When the content of the CFO is equal to or less than the upper limit, favorable cycle performance is likely to be obtained.

Examples of the HCFO include hydrochlorofluoropropene, hydrochlorofluoroethylene and the like. In order to easily control the flammability of the working fluid without significantly decreasing the cycle performance of the working fluid, the HCFO is preferably 1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd) or 1-chloro-1,2-difluoroethylene (HCFO-1122).

One kind of such HCFOs may be used alone or two or more kinds of them may be used in combination.

In a case where the working fluid contains the HCFO, the content of the HCFO is less than 10 mass %, preferably from 1 to 8 mass %, and more preferably from 2 to 5 mass %, based on 100 mass % of the working fluid. When the content of the HCFO is equal to or more than the lower limit, the flammability of the working fluid can be easily controlled. When the content of the HCFO is equal to or less than the upper limit, favorable cycle performance is likely to be obtained.

When the working fluid used in the present invention contains the aforementioned other optional components, the total content of the other optional components in the working fluid is less than 10 mass %, preferably 8 mass % or less, and more preferably 5 mass % or less, based on 100 mass % of the working fluid.

Next, the refrigeration cycle apparatus according to the present embodiment is described.

FIG. 1 is a diagram illustrating the schematic configuration of a refrigeration cycle apparatus 1 in the present embodiment. The refrigeration cycle apparatus 1 includes a circulation path in which the working fluid containing 1,1,2-trifluoroethylene is circulated from a compressor 10 through a condenser 12, an expansion valve 13 and an evaporator 14 back to the compressor 10. In the circulation path, an accumulator 11 is provided between the compressor 10 and the evaporator 14.

The compressor 10 compresses the working fluid (vapor), and refrigerator oil for preventing seizure is stored inside the compressor 10. The refrigerator oil is highly compatible with the working fluid. For example, the refrigerator oil is a polyol ester oil. The accumulator 11 is a liquid reservoir for storing an excess of the refrigerant within the refrigeration cycle due to change in an operating load or the like. The accumulator 11 is provided on the suction side of the compressor 10. The condenser 12 cools and liquefies the working fluid (vapor) discharged from the compressor 10. The expansion valve 13 expands the working fluid (liquid) discharged from the condenser 12. The expansion valve 13 is, for example, an electronic expansion valve which is electrically driven to perform opening/closing operation. The evaporator 14 heats and vaporizes the working fluid (liquid) discharged from the expansion valve 13. The evaporator 14 and the condenser 12 are configured to perform heat exchange between the working fluid and a heat source fluid flowing in opposition or in parallel thereto. The refrigeration cycle apparatus 1 includes a fluid supply unit 15 which supplies a heat source fluid E such as water or air to the evaporator 14, and a fluid supply unit 16 which supplies a heat source fluid F such as water or air to the condenser 12.

The refrigeration cycle apparatus 1 includes various sensors. Specifically, a discharge temperature sensor 33 is provided in a discharge pipe 21, and a suction temperature sensor 34 is provided in a suction pipe 22. The discharge temperature sensor 33 detects the temperature of the refrigerant discharged from the compressor 10. The suction temperature sensor 34 detects the temperature of the refrigerant sucked into the compressor 10. The discharge pressure may be estimated from the temperature detected by the discharge temperature sensor 33 or temperatures of respective portions, or may be detected directly by a discharge pressure sensor 31 provided in the discharge pipe 21. The suction pressure may be estimated from the temperature detected by the suction temperature sensor 34 or temperatures of respective portions, or may be detected directly by a suction pressure sensor 32 provided in the suction pipe 22. In addition, a liquid-side temperature sensor 35 for detecting the temperature of the refrigerant is provided on the liquid side of the condenser 12. Further, the refrigeration cycle apparatus 1 includes a mechanism for adjusting the composition of the working fluid circulating in the refrigeration cycle. The mechanism for adjusting the composition of the working fluid is described later.

In the refrigeration cycle apparatus 1, the following refrigeration cycle is repeated. First, a working fluid vapor A discharged from the evaporator 14 is sucked into the compressor 10 through the accumulator 11. Then, the working fluid vapor A is compressed by the compressor 10 to become a high-temperature and high-pressure working fluid vapor B. The working fluid vapor B discharged from the compressor 10 is cooled and liquefied by the fluid F in the condenser 12 to form a working fluid liquid C. At that time, the fluid F is heated to become a fluid F′, which is discharged from the condenser 12. Successively, the working fluid liquid C discharged from the condenser 12 is expanded by the expansion valve 13 to become a low-temperature and low-pressure working fluid liquid D. Successively, the working fluid liquid D discharged from the expansion valve 13 is heated by the fluid E in the evaporator 14 to become a working fluid vapor A. At that time, the fluid E is cooled to become a fluid E, which is discharged from the evaporator 14.

FIG. 2 is a temperature-entropy chart illustrating the state change of the working fluid in the refrigeration cycle apparatus 1. FIG. 3 is a pressure-enthalpy chart illustrating the state change of the working fluid in the refrigeration cycle apparatus 1. In the following description, FIG. 1 is referred to, if necessary. As illustrated in FIG. 2 and FIG. 3, in the process of a state change from A to B, adiabatic compression is performed by the compressor 10 to change the low-temperature and low-pressure working fluid vapor A to the high-temperature and high-pressure working fluid vapor B. In the process of a state change from B to C, isobaric cooling is performed in the condenser 12 to change the working fluid vapor B to the working fluid C. In the process of a state change from C to D, isenthalpic enthalpy expansion is performed by the expansion valve 13 to change the high-temperature and high-pressure working fluid C to the low-temperature and low-pressure working fluid D. In the process of a state change from D to A, isobaric heating is performed in the evaporator 14 to return the working fluid D to the working fluid vapor A.

The working fluid at G is in a state of saturated liquid. The working fluid at C is in a state of subcooled liquid. When the temperature of the working fluid at G is T3 and the temperature of the working fluid at C is T4, “T3-T4” corresponds to the subcooling degree (subcooling degree) of the working fluid. In addition, the working fluid at H is in a state of saturated vapor. The working fluid at A is in a state of superheated vapor. When the temperature of the working fluid at H is T6 and the temperature of the working fluid at A is T1, “T1-T6” corresponds to the superheating degree of the working fluid.

During the operation of the refrigeration cycle apparatus 1, a part of the refrigerator oil is discharged to the outside of the compressor 10 together with the working fluid (see FIG. 1). During the operation of the refrigeration cycle apparatus 1, the refrigerator oil discharged to the outside of the compressor 10 stays in the accumulator 11 provided on the suction side of the compressor and the like. FIG. 4 is a view of the schematic configuration of the accumulator 11. As illustrated in FIG. 4, the accumulator 11 includes a casing 51 having a sealing structure, an inlet pipe 52, and an outlet pipe 53. The inlet pipe 52 is inserted into the casing 51 from above, and an opening end of the inlet pipe 52 is open to the upper inside of the casing 51. The outlet pipe 53 is inserted into the casing 51 from above. The outlet pipe 53 has a bent portion which is bent like a substantially U-shape in a portion close to a bottom portion inside the casing 51. An opening end of the outlet pipe 53 is open to an upper portion of the casing 51. An oil returning hole 54 is provided in the bent portion of the outlet pipe 53 in order to prevent a fixed amount or more of the refrigerator oil from staying. In addition, a band-like heater 55 is wound on the outer circumference of the casing 51.

During the operation of the refrigeration cycle apparatus 1, the working fluid is dissolved into the refrigerator oil staying outside the compressor, e.g. in the accumulator 11 or the like. When the working fluid contains HFO-1123 and a component other than FIFO-1123, the component other than FIFO-1123 may have a higher degree of solubility to the refrigerator oil than HFO-1123 depending on the kind of the component other than HFO-1123 when the temperature of the refrigerator oil is low. In such a case, for example, when the ambient temperature is low during the operation, the component other than HFO-1123 is selectively dissolved into the refrigerator oil which has been cooled down to a low temperature by the ambient air. That is, during the operation of the refrigeration cycle apparatus 1, the proportion of HFO-1123 in the working fluid circulating within the refrigeration cycle may be increased due to change in conditions such as the ambient temperature.

During the operation of the refrigeration cycle apparatus 1, a liquid refrigerant tends to stay at a place such as the accumulator 11. In addition, in the place where a liquid refrigerant tends to stay, e.g. in the accumulator 11, a high-boiling-point refrigerant component of the working fluid stays as a liquid refrigerant more easily than a low-boiling-point refrigerant component of the working fluid. Table 2 shows boiling points of representative candidates of refrigerant components including HFO-1123 and others. Among the refrigerants shown in Table 2, HFO-1123 has the lowest boiling point. During the operation of the refrigeration cycle apparatus 1, the components other than HFO-1123 stay as liquid refrigerants in the accumulator more easily than HFO-1123 when HFO-1123 has the lowest boiling point among the refrigerant components in the working fluid. As a result, the proportion of HFO-1123 in the working fluid circulating within the refrigeration cycle may be increased.

TABLE 2 Kind of refrigerant HFC HFO HFC- HFC- HFC- HFC- HFC- HFC- HFO- HFO- HFO- HFO- 32 152a 143a 134 134a 125 1123 1234yf 1234ze(E) 1234ze(Z) Boiling −51.7 −24 −47.2 −23 −26.1 −48.1 −56 −29.4 −19 9.8 point (° C.)

When the proportion of HFO-1123 in the working fluid circulating within the refrigeration cycle is increased, the risk that the disproportionation reaction of HFO-1123 occurs increases. When the proportion of HFO-1123 in the composition of the working fluid increases, adjustment must be performed by the mechanism for adjusting the composition of the working fluid so that the proportion of HFO-1123 in the composition of the working fluid falls within a fixed range in order to prevent the disproportionation reaction of HFO-1123. When the proportion of HFO-1123 in the composition of the working fluid falls within the fixed range, the composition of the working fluid is referred to as a steady composition.

Here, description is made about the mechanism for adjusting the composition of the working fluid circulating within the refrigeration cycle, and the mechanism is a characterizing portion in the present invention.

FIG. 5 is a block diagram illustrating the schematic configuration of a composition adjustment mechanism 40 which adjusts the composition of the working fluid circulating within the refrigeration cycle. As illustrated in FIG. 5, the composition adjustment mechanism 40 includes a composition change detection unit 41 which detects the change of the composition of the working fluid from the steady composition, a composition adjustment unit 42 which adjusts the composition of the working fluid, and a control unit 43 which controls the composition adjustment unit 42. The control unit 43 controls the composition adjustment unit 42 based on a detection result obtained by the composition change detection unit 41.

As illustrated in FIG. 1, the discharge temperature sensor 33 is used as the composition change detection unit 41 in the refrigeration cycle apparatus 1. The discharge temperature sensor 33 is attached to the discharge pipe 21 which connects the compressor 10 and the condenser 12, and detects the discharge temperature of the compressor 10. When components other than HFO-1123 in the working fluid are selectively dissolved into the refrigerator oil in the refrigeration cycle apparatus 1, there appears a similar behavior to that in the case where the amount of the working fluid is insufficient. Thus, the discharge temperature increases.

In addition, when a large amount of a liquid refrigerant having a high proportion of the components other than HFO-1123 stays at a place where a liquid refrigerant tends to stay, e.g. in the accumulator 11, there appears a similar behavior to that in the case where the amount of the working fluid is insufficient. Thus, the discharge temperature increases. When the temperature detected by the discharge temperature sensor 33 exceeds a predetermined temperature, it is judged that the composition of the working fluid is changed from the steady composition.

As illustrated in FIG. 1, the composition adjustment unit 42 is the heater 55 attached to the accumulator 11. When the composition change detection unit 41 judges that the composition of the working fluid is changed from the steady composition, the control unit 43 allows electric current to flow through the heater 55.

For example, when the condensation temperature of FIFO-1123 is lower than those of any other components in the working fluid containing HFO-1123, the amount of the other components dissolved in the refrigerator oil staying in the accumulator 11 may be larger than the amount of HFO-1123 dissolved in the refrigerator oil, so that the proportion of HFO-1123 in the working fluid circulating in the circulation path of the refrigeration cycle apparatus 1 may increase. Even in such a case, the refrigerator oil staying in the accumulator 11 is heated by the heater 55 through which electric current flows. Thus, the refrigerant components which have been dissolved in the refrigerator oil are turned out so that the composition of the working fluid circulating in the circulation path of the refrigeration cycle apparatus 1 can be returned to the steady composition. As a result, it is possible to effectively prevent occurrence of disproportionation reaction of HFO-1123 when a working fluid containing HFO-1123 is used.

Further, for example, when HFO-1123 has the lowest boiling point among refrigerant components in the working fluid, a large amount of a liquid refrigerant having a high proportion of the components other than HFO-1123 may stay in the accumulator 11, so that the proportion of HFO-1123 in the working fluid circulating in the circulation path of the refrigeration cycle apparatus 1 may increase. Even in such a case, the liquid refrigerant having a high proportion of the components other than HFO-1123 and staying in the accumulator 11 is evaporated by allowing electric current to flow through the heater 55. Thus, the composition of the working fluid circulating in the circulation path of the refrigeration cycle apparatus 1 can be returned to the steady composition. As a result, it is possible to effectively prevent occurrence of disproportionation reaction of HFO-1123 when a working fluid containing HFO-1123 is used.

MODIFICATION EXAMPLE 1

A superheat detection unit 70 which detects the superheating degree of the working fluid sucked into the compressor 10 may be used as the composition change detection unit 41 (see FIG. 5). FIG. 6 is a diagram for explaining the superheat detection unit 70 as the composition change detection unit 41 in a refrigeration cycle apparatus 101. Constituent elements shared with those in FIG. 1 are referenced correspondingly, and description thereof is omitted. As illustrated in FIG. 6, for example, when the suction pressure sensor 32 is provided in the suction pipe 22, the superheat detection unit 70 detects the superheating degree by deriving a saturated vapor temperature T6 (see FIG. 3) from a suction pressure Ps (see FIG. 3) detected by the suction pressure sensor 32, and subtracting the saturated vapor temperature T6 from a temperature value (Ti) detected by the suction temperature sensor 34. When the suction pressure sensor 32 is not provided in the suction pipe 22, the suction pressure Ps used for detecting the superheating degree is estimated from the suction temperature sensor 34 or temperatures of respective portions as described previously. When the components other than HFO-1123 in the working fluid are selectively dissolved in the refrigerator oil in the refrigeration cycle apparatus 101, there appears a similar behavior to that in the case where the amount of the working fluid is insufficient. Thus, the superheating degree increases. In addition, in the refrigeration cycle apparatus 101, when a large amount of a liquid refrigerant having a high proportion of the components other than HFO-1123 stays at a place where a liquid refrigerant tends to stay, e.g. in the accumulator 11, there appears a similar behavior to that in the case where the amount of the working fluid is insufficient. Thus, the superheating degree increases. When the superheating degree detected by the superheat detection unit 70 exceeds a predetermined value, it is judges that the composition of the working fluid is changed from the steady composition. The predetermined temperature is decided based on the superheating degree during the stable operation of the refrigeration cycle apparatus 101 in which the composition of the working fluid is the steady composition.

MODIFICATION EXAMPLE 2

A subcool detection unit 80 which detects the subcooling degree of the working fluid at the outlet of the condenser 12 may be used as the composition change detection unit 41 (see FIG. 5). FIG. 7 is a diagram for explaining the subcool detection unit 80 as the composition change detection unit 41 in a refrigeration cycle apparatus 201. Constituent elements shared with those in FIG. 1 are referenced correspondingly, and description thereof is omitted. As illustrated in FIG. 7, for example, when the discharge pressure sensor 31 is provided in the discharge pipe 21, the subcool detection unit 80 detects the subcooling degree by deriving a saturated liquid temperature T3 (see FIG. 3) from a discharge pressure Pd (see FIG. 3) in the compressor 10 detected by the discharge pressure sensor 31, and subtracting the saturated liquid temperature T3 from a temperature value (T4) detected by the liquid-side temperature sensor 35. When the discharge pressure sensor 31 is not provided in the discharge pipe 21, the discharge pressure Pd used for detecting the subcooling degree is estimated from the discharge temperature sensor 33 or temperatures of respective portions as described previously. When the components other than HFO-1123 in the working fluid are selectively dissolved in the refrigerator oil, there appears a similar behavior to that in the case where the amount of the working fluid is insufficient. In addition, in the refrigeration cycle apparatus 201, when a large amount of a liquid refrigerant having a high proportion of the components other than HFO-1123 stays at a place where a liquid refrigerant tends to stay, e.g. in the accumulator 11, there appears a similar behavior to that in the case where the amount of the working fluid is insufficient. When the subcooling degree detected by the subcool detection unit 80 is deviated from a predetermined range, it is judged that the composition of the working fluid is changed from the steady composition. The predetermined range is decided based on the subcooling degree during the stable operation of the refrigeration cycle apparatus 201 in which the composition of the working fluid is the steady composition.

MODIFICATION EXAMPLE 3

The composition adjustment unit 42 (see FIG. 5) may be a hot gas introduction unit 60 which introduces a hot gas discharged from the compressor 10 into an accumulator 111. FIG. 8 is a diagram for explaining the hot gas introduction unit 60 in a refrigeration cycle apparatus 301. Constituent elements shared with those in FIG. 1 are referenced correspondingly, and description thereof is omitted. As illustrated in FIG. 8, the hot gas introduction unit 60 includes a hot gas bypass 61, and an on-off valve 62. Due to the hot gas bypass 61, a part of the hot gas discharged from the compressor 10 is diverted and introduced into the accumulator 111. The on-off valve 62 is provided in the hot gas bypass 61. The on-off valve 62 is normally closed. When the composition change detection unit 41 judges that the composition of the working fluid is changed, the control unit 43 controls the on-off valve 62 so as to change a state of the on-off valve 62 from a closed state to an open state. FIG. 9 is a view of the schematic configuration of the accumulator 111 to which the hot gas bypass 61 is connected. Constituent elements shared with those in FIG. 4 are referenced correspondingly, and description thereof is omitted. As illustrated in FIG. 9, the hot gas bypass 61 is connected to the casing 51 so that the hot gas can be introduced into the accumulator 111.

For example, when the condensation temperature of HFO-1123 is lower than those of any other components in the working fluid containing HFO-1123, the amount of the other components dissolved in the refrigerator oil staying in the accumulator 111 may be larger than the amount of HFO-1123 dissolved in the refrigerator oil, so that the proportion of HFO-1123 in the working fluid circulating in the circulation path of the refrigeration cycle apparatus 301 may increase. Even in such a case, the refrigerator oil staying in the accumulator 111 is heated by the hot gas. Thus, the refrigerant components which have been dissolved in the refrigerator oil can be turned out. As a result, the composition of the working fluid can be returned to the steady composition.

Further, for example, when HFO-1123 has the lowest boiling point among refrigerant components in the working fluid, a large amount of a liquid refrigerant having a high proportion of the components other than HFO-1123 may stay in the accumulator 111, so that the proportion of HFO-1123 in the working fluid circulating in the circulation path of the refrigeration cycle apparatus 301 may increase. Even in such a case, the liquid refrigerant having a high proportion of the components other than HFO-1123 and staying in the accumulator 111 is heated and evaporated by the hot gas. Thus, the composition of the working fluid circulating in the circulation path of the refrigeration cycle apparatus 301 can be returned to the steady composition. As a result, it is possible to effectively prevent occurrence of disproportionation reaction of HFO-1123 when a working fluid containing HFO-1123 is used.

MODIFICATION EXAMPLE 4

The composition adjustment unit 42 (see FIG. 5) may be the compressor 10 (a motor which drives a compression mechanism of the compressor 10). FIG. 10 is a diagram for explaining the composition adjustment unit 42 in a refrigeration cycle apparatus 401. Constituent elements shared with those in FIG. 1 are referenced correspondingly, and description thereof is omitted.

As illustrated in FIG. 10, the composition adjustment unit 42 is a motor which drives a compression mechanism of the compressor 10. When the composition change detection unit 41 judges that the composition of the working fluid is changed, the control unit 43 controls the compressor 10 so as to increase the number of revolutions of the motor in the compressor 10.

For example, when the condensation temperature of HFO-1123 is lower than those of any other components in the working fluid containing HFO-1123, the amount of the other components dissolved in the refrigerator oil staying in the accumulator 11 may be larger than the amount of HFO-1123 dissolved in the refrigerator oil, so that the proportion of HFO-1123 in the working fluid circulating in the circulation path of the refrigeration cycle apparatus 401 may increase. Even in such a case, when the number of revolutions of the motor in the compressor 10 is increased, the flow velocity of the working fluid circulating within the refrigeration cycle apparatus 401 increases so that, of the refrigerator oil discharged to the outside of the compressor 10 and staying in the accumulator 11, the amount of a part returned to the compressor 10 can be increased. The refrigerator oil returned to the compressor 10 is heated inside the compressor 10 so that the refrigerant components which have been dissolved in the refrigerator oil can be turned out. As a result, the composition of the working fluid circulating can be returned to the steady composition.

MODIFICATION EXAMPLE 5

The composition adjustment unit 42 (see FIG. 5) may be the expansion valve 13. FIG. 11 is a diagram for explaining the composition adjustment unit 42 in a refrigeration cycle apparatus 501. Constituent elements shared with those in FIG. 1 are referenced correspondingly, and description thereof is omitted. As illustrated in FIG. 11, the composition adjustment unit 42 is the expansion valve 13. When the composition change detection unit 41 judges that the composition of the working fluid is changed, the control unit 43 controls the expansion valve 13 so as to increase the opening degree of the expansion valve 13.

For example, when the condensation temperature of HFO-1123 is lower than those of any other components in the working fluid containing HFO-1123, the amount of the other components dissolved in the refrigerator oil staying in the accumulator 11 may be larger than the amount of HFO-1123 dissolved in the refrigerator oil, so that the proportion of HFO-1123 in the working fluid circulating in the circulation path of the refrigeration cycle apparatus 501 may increase. Even in such a case, when the opening degree of the expansion valve 13 is increased, the flow velocity of the working fluid circulating within the refrigeration cycle apparatus 501 increases so that, of the refrigerator oil discharged to the outside of the compressor 10 and staying in the accumulator 11, the amount of a part returned to the compressor 10 can be increased. The refrigerator oil returned to the compressor 10 is heated inside the compressor 10 so that the refrigerant components which have been dissolved in the refrigerator oil can be turned out. As a result, the composition of the working fluid circulating can be returned to the steady composition.

MODIFICATION EXAMPLE 6

When the refrigeration cycle apparatus is, for example, a large-sized air conditioner, the refrigeration cycle apparatus typically has a configuration in which a receiver for storing an excess of a working fluid is provided between the condenser and the expansion valve. The composition adjustment unit 42 (see FIG. 5) may be a liquid refrigerant returning unit by which the liquid refrigerant stored in the receiver is returned to an intermediate pressure portion of the compressor. FIG. 12 is a diagram for explaining a liquid refrigerant returning means 90 in a refrigeration cycle apparatus 601. Constituent elements shared with those in FIG. 1 are referenced correspondingly, and description thereof is omitted. As illustrated in FIG. 12, the liquid refrigerant returning unit 90 includes a liquid refrigerant bypass 91 for extracting a liquid refrigerant stored in the receiver 17 and injecting the liquid refrigerant to the intermediate pressure portion of the compressor 10 through an auxiliary expansion valve 92. The auxiliary expansion valve 92 decompresses and expands the refrigerant passing through the liquid refrigerant bypass 91. The auxiliary expansion valve 92 is, for example, constituted by an electronic expansion valve. The auxiliary expansion valve 92 is normally closed. When the composition change detection unit 41 judges that the composition of the working fluid is changed, the control unit 43 controls the auxiliary expansion valve 92 so as to increase the opening degree of the auxiliary expansion valve 92.

For example, when HFO-1123 has the lowest boiling point among refrigerant components in the working fluid, a large amount of a liquid refrigerant having a high proportion of the components other than HFO-1123 may stay in the receiver 17, so that the proportion of HFO-1123 in the working fluid circulating in the circulation path of the refrigeration cycle apparatus 601 may increase. Even in such a case, when the control unit 43 controls the auxiliary expansion valve 92 so as to increase the opening degree of the auxiliary expansion valve 92, the liquid refrigerant having a high proportion of the components other than HFO-1123 and staying in the receiver 17 is decompressed and expanded by the auxiliary expansion valve 92, and then, injected into the intermediate pressure portion of the compressor 10.

The liquid refrigerant having a high proportion of the components other than HFO-1123 and injected into the intermediate pressure portion of the compressor 10 is compressed again by the compressor 10, and discharged as a high-temperature and high-pressure gas refrigerant. Thus, the composition of the working fluid circulating in the circulation path of the refrigeration cycle apparatus 601 can be returned to the steady composition. As a result, it is possible to effectively prevent occurrence of disproportionation reaction of HFO-1123 when a working fluid containing HFO-1123 is used.

The present invention is not limited to the aforementioned embodiments, but may be changed suitably without departing from the gist of the present invention. In addition, the aforementioned Modification examples may be combined with one another suitably. For example, the composition change detection unit in Modification example 1 or 2 may be used as the composition change detection unit in Modification example 3. The composition change detection unit in Modification example 1 or 2 may be used as the composition change detection unit in Modification example 4. The composition change detection unit in Modification example 1 or 2 may be used as the composition change detection unit in Modification example 5. The composition change detection unit in Modification example 1 or 2 may be used as the composition change detection unit in Modification example 6.

Further, the method in which a liquid refrigerant stored is heated and evaporated by allowing electric current to flow through a heater or introducing a hot gas may be applied to a place (hereinafter, referred to as liquid refrigerant staying place) other than the accumulator where the liquid refrigerant tends to stay within the refrigeration cycle apparatus, in the same manner as in the aforementioned embodiments described previously using the accumulator by way of example. That is, when the composition change detection unit detects that the composition of the working fluid is changed from the steady composition, by allowing electric current to flow through the heater attached to the liquid refrigerant staying place or introducing the hot gas to the liquid refrigerant staying place, the liquid refrigerant staying at the liquid refrigerant staying place is heated. Thus, the composition of the working fluid can be returned to the steady composition.

Furthermore, the aforementioned embodiments are described as to the case where the components other than HFO-1123 are selectively dissolved in the refrigerator oil during the operation of the refrigeration cycle apparatus. However, there is a case where the components other than HFO-1123 may be selectively dissolved in the refrigerator oil staying in a crank case of the compressor even under the suspension of the refrigeration cycle apparatus. Even in the case where the components other than HFO-1123 are selectively dissolved in the refrigerator oil staying in the crank case of the compressor under the suspension of the refrigeration cycle apparatus, the proportion of HFO-1123 in the working fluid circulating within the refrigeration cycle may increase as soon as the operation of the refrigeration cycle apparatus is resumed. Thus, the risk that occurrence of disproportionation reaction of HFO-1123 may occur is increased. In this case, before the operation of the refrigeration cycle apparatus is resumed, the refrigerator oil staying in the crank case may be heated by a crank case heater or the like to thereby turn out the refrigerant components dissolved in the refrigerator oil. Thus, the composition of the working fluid can be returned to the steady composition.

Although the present invention has been described in detail and along its specific embodiments, it is obvious for those skilled in the art that various changes or modifications can be made on the present invention without departing from the spirit and scope of the present invention. The present application is based on a Japanese patent application No. 2016-32692 filed on Feb. 24, 2016, the contents of which are incorporated herein by reference.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

1 Refrigeration cycle apparatus

10 Compressor

11 Accumulator

12 Condenser

13 Expansion valve

14 Evaporator

40 Composition adjustment mechanism

41 Composition change detection unit

42 Composition adjustment unit

43 Control unit 

1. A refrigeration cycle apparatus comprising a circulation path in which a working fluid containing 1,1,2-trifluoroethylene is circulated from a compressor through a condenser, an expansion valve and an evaporator back to the compressor, the refrigeration cycle apparatus comprising: a composition change detection unit which detects a change of a composition of the working fluid from a steady composition thereof; a composition adjustment unit which adjusts the composition of the working fluid; and a control unit which controls the composition adjustment unit, wherein the control unit controls the composition adjustment unit based on a detection result obtained by the composition change detection unit.
 2. The refrigeration cycle apparatus according to claim 1, wherein the composition change detection unit is a discharge temperature sensor which detects a discharge temperature of the compressor, and judges that the composition of the working fluid is changed from the steady composition when the discharge temperature detected by the discharge temperature sensor exceeds a predetermined temperature.
 3. The refrigeration cycle apparatus according to claim 1, wherein the composition change detection unit is a superheat detection unit which detects a superheating degree of the working fluid sucked into the compressor, and judges that the composition of the working fluid is changed when the superheating degree detected by the superheat detection unit exceeds a predetermined value.
 4. The refrigeration cycle apparatus according to claim 1, wherein the composition change detection unit is a supercool detection unit which detects a supercooling degree of the working fluid sucked into the compressor, and judges that the composition of the working fluid is changed when the supercooling degree detected by the supercool detection unit is deviated from a predetermined range.
 5. The refrigeration cycle apparatus according to claim 1, further comprising: an accumulator provided between the evaporator and the compressor in the circulation path for storing an excess of the working fluid, wherein the composition adjustment unit is a heater attached to the accumulator, and wherein the control unit allows electric current to flow through the heater when the composition change detection unit judges that the composition of the working fluid is changed.
 6. The refrigeration cycle apparatus according to claim 1, further comprising: an accumulator provided between the evaporator and the compressor in the circulation path for storing an excess of the working fluid, wherein the composition adjustment unit includes: a hot gas bypass which diverts a part of a hot gas discharged from the compressor and introduces the diverted hot gas into the accumulator; and an on-off valve provided in the hot gas bypass, and wherein the control unit controls the on-off valve so as to change a state of the on-off valve from a closed state to an open state when the composition change detection unit judges that the composition of the working fluid is changed.
 7. The refrigeration cycle apparatus according to claim 1, wherein the composition adjustment unit is a motor which drives a compression mechanism of the compressor, and the control unit controls the motor so as to increase the number of revolutions of the motor when the composition change detection unit judges that the composition of the working fluid is changed.
 8. The refrigeration cycle apparatus according to claim 1, wherein the composition adjustment unit is the expansion valve, and the control unit controls the expansion valve so as to increase an opening degree of the expansion valve when the composition change detection unit judges that the composition of the working fluid is changed.
 9. The refrigeration cycle apparatus according to claim 1, further comprising: a receiver provided between the condenser and the expansion valve in the circulation path for storing an excess of the working fluid, wherein the composition adjustment unit includes a liquid refrigerant bypass for extracting a liquid refrigerant stored in the receiver and injecting the extracted liquid refrigerant to an intermediate pressure portion of the compressor through an auxiliary expansion valve, and wherein the control unit controls the auxiliary expansion valve so as to increase an opening degree of the auxiliary expansion valve when the composition change detection unit judges that the composition of the working fluid is changed.
 10. The refrigeration cycle apparatus according to claim 2, further comprising: an accumulator provided between the evaporator and the compressor in the circulation path for storing an excess of the working fluid, wherein the composition adjustment unit is a heater attached to the accumulator, and wherein the control unit allows electric current to flow through the heater when the composition change detection unit judges that the composition of the working fluid is changed.
 11. The refrigeration cycle apparatus according to claim 3, further comprising: an accumulator provided between the evaporator and the compressor in the circulation path for storing an excess of the working fluid, wherein the composition adjustment unit is a heater attached to the accumulator, and wherein the control unit allows electric current to flow through the heater when the composition change detection unit judges that the composition of the working fluid is changed.
 12. The refrigeration cycle apparatus according to claim 4, further comprising: an accumulator provided between the evaporator and the compressor in the circulation path for storing an excess of the working fluid, wherein the composition adjustment unit is a heater attached to the accumulator, and wherein the control unit allows electric current to flow through the heater when the composition change detection unit judges that the composition of the working fluid is changed.
 13. The refrigeration cycle apparatus according to claim 2, further comprising: an accumulator provided between the evaporator and the compressor in the circulation path for storing an excess of the working fluid, wherein the composition adjustment unit includes: a hot gas bypass which diverts a part of a hot gas discharged from the compressor and introduces the diverted hot gas into the accumulator; and an on-off valve provided in the hot gas bypass, and wherein the control unit controls the on-off valve so as to change a state of the on-off valve from a closed state to an open state when the composition change detection unit judges that the composition of the working fluid is changed.
 14. The refrigeration cycle apparatus according to claim 3, further comprising: an accumulator provided between the evaporator and the compressor in the circulation path for storing an excess of the working fluid, wherein the composition adjustment unit includes: a hot gas bypass which diverts a part of a hot gas discharged from the compressor and introduces the diverted hot gas into the accumulator; and an on-off valve provided in the hot gas bypass, and wherein the control unit controls the on-off valve so as to change a state of the on-off valve from a closed state to an open state when the composition change detection unit judges that the composition of the working fluid is changed.
 15. The refrigeration cycle apparatus according to claim 4, further comprising: an accumulator provided between the evaporator and the compressor in the circulation path for storing an excess of the working fluid, wherein the composition adjustment unit includes: a hot gas bypass which diverts a part of a hot gas discharged from the compressor and introduces the diverted hot gas into the accumulator; and an on-off valve provided in the hot gas bypass, and wherein the control unit controls the on-off valve so as to change a state of the on-off valve from a closed state to an open state when the composition change detection unit judges that the composition of the working fluid is changed.
 16. The refrigeration cycle apparatus according to claim 2, wherein the composition adjustment unit is a motor which drives a compression mechanism of the compressor, and the control unit controls the motor so as to increase the number of revolutions of the motor when the composition change detection unit judges that the composition of the working fluid is changed.
 17. The refrigeration cycle apparatus according to claim 3, wherein the composition adjustment unit is a motor which drives a compression mechanism of the compressor, and the control unit controls the motor so as to increase the number of revolutions of the motor when the composition change detection unit judges that the composition of the working fluid is changed.
 18. The refrigeration cycle apparatus according to claim 4, wherein the composition adjustment unit is a motor which drives a compression mechanism of the compressor, and the control unit controls the motor so as to increase the number of revolutions of the motor when the composition change detection unit judges that the composition of the working fluid is changed.
 19. The refrigeration cycle apparatus according to claim 2, wherein the composition adjustment unit is the expansion valve, and the control unit controls the expansion valve so as to increase an opening degree of the expansion valve when the composition change detection unit judges that the composition of the working fluid is changed.
 20. The refrigeration cycle apparatus according to claim 3, wherein the composition adjustment unit is the expansion valve, and the control unit controls the expansion valve so as to increase an opening degree of the expansion valve when the composition change detection unit judges that the composition of the working fluid is changed. 